Niobium oxide supported

Sasaki K, Zhang L, Adzic RR. 2008. Niobium oxide-supported platinum ultra-low amount electrocatalysts for oxygen reduction. Phys Chem Chem Phys 10 159-167. 

Catalysts containing niobia supported on various oxides have been the subject of considerable recent interest [1-4]. The molecular structures and reactivity of niobium oxides supported on alumina, titania, zirconia and silica have been intensively investigated over the last few years. Niobia supported on silica has been shown to be active for the dehydrogenation and dehydration of alcohols, photo-oxidation of propene and oxidative decomposition of methyl tertiary butyl ether. Titania supported niobia is active for the selective catalytic reduction (SCR) of NO by NH3. 

Oxidative dehydrogenation of ethane over vanadium and niobium oxides supported catalysts... 

In this work, the activity and selectivity of catalysts based on niobium and vanadium oxides supported on high surface area anatase Ti02 in ethane ODH have been investigated. Specifically, the influence of the cooperation of vanadium and niobium oxides supported phases as components inducing respectively redox and acid properties, together with the effect of the preparation conditions on the catal3dic performances have been studied. 

The formation of 1-butene and 2-butenes from ethene is initiated on niobium oxide by irradiation, though this oxide is catalytically inactive for the reaction under dark. Fig.1 shows the induction of the catalytic activity for the formation of butenes from ethene on niobium oxide supported on porous Vycor glass(Nb205/PVG) by irradiation for lOmin. The amount of 2-... 

Datka, J. Turek, A.M. Jehng, J.M. Wachs, I.E. Acidic properties of supported niobium oxide catalysts An infrared spectroscopy investigation. J. Catal. 1992, 35, 186-199. 

Antonelli and co-workers have recently demonstrated that room temperature stoichiometric ammonia synthesis is possible with their mesoporous titanium and niobium oxide catalysts. In this study, they proposed that the ammonia species are formed via the reaction activated nitrogen with the underlying moisture of the support. Reversible, inter-conversion of and NH2 species via exposure to moist air for aluminophosphate oxynitride catalysts has been observed by FTIR and XPS by Marquez and co-workers. There has been a lot of interest in the literature in the development of novel routes for the low temperature stoichiometric conversion of nitrogen to ammonia, e.g.. However, in principle this could be realised by the nitridation of Li, followed by hydrolysis, although the kinetics would be very slow. 

The group 5-7 supported transition metal oxides (of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and rhenium) are characterized by terminal oxo bonds (M =0) and bridging oxygen atoms binding the supported oxide to the cation of the support (M -0-MSUpport). The TOF values for ODH of butane or ethane on supported vanadia were found to depend strongly on the specific oxide support, varying by a factor of ca. 50 (titania > ceria > zirconia > niobia > alumina > silica). 

The aqueous preparation oT supported niobium oxide catalysts was developed by using niobium oxalate as a precursor. The molecular states oT aqueous niobium oxalate solutions were investigated by Raman spectroscopy as a -function o-f pH. The results show that two kinds o-f niobium ionic species exist in solution and their relative concentrations depend on the solution pH and the oxalic acid concentration. The supported niobium oxide catalysts were prepared by the incipient wetness impregnation technique and characterized by Raman, XRD, XPS, and FTIR as a -function o-f niobium oxide coverage and calcination temperature. The Raman studies reveal that two types o-f sur-face niobium oxide species exist on the alumina support and their relative concentrations depend on niobium oxide coverage. Raman, XRD, XPS, and FTIR results indicate that a monolayer oT sur-face niobium oxide corresponds to 19%... 

Supported niobium oxide catalysts have recently been shown to be e-f-fective catalysts Tor many catalytic reactions pollution abatement, selective oxidation,... 

Niobium ethoxide [Nb(0C2H5)g] has traditionally been used as a precursor Tor the preparation oT supported niobium oxide catalysts. This non-aqueous preparation... 

The crystalline Nb205 phase in the supported niobium oxide catalysts was detected by an APD 3600 automated X-... 

The CO2 uptake of supported niobium oxide on AI2O3 at different Nb205 loadings was measured with a Quantasorb BET apparatus using a 1 9 ratio of C02/He mixture gases. The samples were degassed at 250 C for 2 hours under flowing He, and the CO2 chemisorption was performed at room temperature. 

A series of supported niobium oxide on alumina catalysts, 0-45% Nb205/Al203, were further characterized by XRD, XPS, CO2 chemisorption, as well as Raman spectroscopy in order to determine the monolayer content of the Nb205/Al203 system. The transition from a two-dimensional metal oxide overlayer to three-dimensional metal oxide particles can be detected by monitoring the... 

Niobium oxide (niobia) is an active catalyst, and can be used as a support for metal nanoparticles or oxides, and it can serve as a promoter in some reactions ([43 5] and references therein). Catalytic applications of niobia include the Fischer-Tropsch synthesis, oxidative dehydrogenation of alkanes, and oxidative coupling of methane. Studies on high-surface-area niobium oxides are complicated by a high degree of complexity because several stable structures (NbO, NbO and Nb O ) exist and the resulting surfaces of high-surface-area niobium oxides are not simple truncations of bulk niobia structures. This is even more so for supported metal oxides when two-dimensional thin films of niobium oxide partially cover a support oxide (Al Oj, SiOj, ZrOj, TiOj, [43]). Nb Oj was also used as a support for V, Cr, Re, Mo, and W oxide overlayers [45, 46]. 

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